Re: [PATCH bpf-next v2 1/7] samples: bpf: refactor hbm program with libbpf

["Daniel T. Lee" <danieltimlee@gmail.com>]

Sorry for the late reply.

On Sat, Nov 21, 2020 at 11:34 AM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Thu, Nov 19, 2020 at 03:06:11PM +0000, Daniel T. Lee wrote:
> [ ... ]
>
> >  static int run_bpf_prog(char *prog, int cg_id)
> > [ ... ]
> >       if (!outFlag)
> > -             type = BPF_CGROUP_INET_INGRESS;
> > -     if (bpf_prog_attach(bpfprog_fd, cg1, type, 0)) {
> > -             printf("ERROR: bpf_prog_attach fails!\n");
> > -             log_err("Attaching prog");
> > +             bpf_program__set_expected_attach_type(bpf_prog, BPF_CGROUP_INET_INGRESS);
> > +
> > +     link = bpf_program__attach_cgroup(bpf_prog, cg1);
> > +     if (libbpf_get_error(link)) {
> > +             fprintf(stderr, "ERROR: bpf_program__attach_cgroup failed\n");
> > +             link = NULL;
> Again, this is not needed.  bpf_link__destroy() can
> handle both NULL and error pointer.  Please take a look
> at the bpf_link__destroy() in libbpf.c
>
> > +             goto err;
> > +     }
> > [ ... ]

> > @@ -398,10 +400,10 @@ static int run_bpf_prog(char *prog, int cg_id)
> >  err:
> >       rc = 1;
> >
> > -     if (cg1)
> > -             close(cg1);
> > +     bpf_link__destroy(link);
> > +     close(cg1);
> >       cleanup_cgroup_environment();
> > -
> > +     bpf_object__close(obj);
> The bpf_* cleanup condition still looks wrong.
>
> I can understand why it does not want to cleanup_cgroup_environment()
> on the success case because the sh script may want to run test under this
> cgroup.
>
> However, the bpf_link__destroy(), bpf_object__close(), and
> even close(cg1) should be done in both success and error
> cases.
>
> The cg1 test still looks wrong also.  The cg1 should
> be init to -1 and then test for "if (cg1 == -1)".

Thanks for pointing this out.
I'll remove NULL initialize and fix this on the next patch.


--
Best,
Daniel T. Lee